Method of making hollow-walled flush tanks



Aug. 16, 1960 J. 5. CLIFFORD 2,948,902

METHOD OF MAKING HOLLOW-WALLED FLUSH TANKS Filed Feb. 8. 1954 y Q I, '20

I fi W IE) i Mi I 1 W1 1 M W I W 5 L L J0/m52 L United States Patent NIETHOD OF MAKING HOLLOW-WALLED FLUSH TANKS John S. Clifford, Woodstock, 11]., assignor to Chicago Pottery Company, Chicago, 111., a corporation of Delaware Filed Feb. 8, 1954, Ser. No. 408,696 Claims. (Cl. 4-68) My invention relates generally to a new and improved method of making ceramic articles having hollow walls. More particularly, the invention relates to a new and practical method of making hollow-walled flush tanks or water closets.

Hollow-walled flush tanks for toilets which would be non-sweating would be very desirable. known that the sweat or condensation which forms on such tanks is a considerable nuisance. However, insofar as I am aware, no practical method of making such hollowwalled, non-sweating flush tanks has been proposed which would permit such flush tanks to bemanufactured on a quantity production basis so as to compete favorably with the ordinary solid-walled flush tank.

The broad concept and technique of making hollowcast ceramic articles is in itself broadly old and known. In general, the hollow casting technique involves filling a plaster mold with slip and allowing the mold to stand until the slip has set or deposited against the absorbent surfaces of the mold but remains in a liquid condition on the interior, whereupon the fluid slip is tapped or drained off from the interior so as to provide a hollow-walled ceramic casting. When it was attempted to apply this hollow-casting technique in the usual way to the manufacture of flush tanks or water closets, it was found that the technique could not be practiced successfully for'sev eral reasons.

I have found, in accordance with the present invention,

that by proceeding in a particular manner it is possible and practical to produce hollow-walled flush tanks on a commercial scale. Briefly, the present invention involves, first of all, casting the outer shell or outer wall of a water closet or flush tank in the usual manner, and then withdrawing the core and inserting a second and smaller core which defines the inner wall of the hollow-walled flush tank. After the second core is inserted with the first casting or pre-cast of the outer shell remaining in the mold, the second mold cavity is filled with slip 'and after setting sufiiciently for the slip to build up on the surface of the second core, the mold is tapped and the liquid slip on the interior of the casting is drained ofi.

Accordingly, one object of the invention, generally stated, is a new and improved method of making hollowwalled ceramic articles, particularly flush tanks and the like, which permits such articles to be manufactured on a quantity production basis with very few failures or rejects.

More specifically, an object of the invention is a new and improved method of producing hollow-walled flush tanks or water closets wherein the outer shell or wall of the tank is first cast with the desired thickness in the usual manner employed for producing single-walled flush tanks and then the first core is replaced by a second and smaller core which defines the inner wall of the hollow tank, and the mold is again filled with slip and allowed to stand until the inner wall of the tank has been formed whereupon the liquid slip is drained off so as to leave a hollowwalled casting.

It is commonly r 2,948,902 Patented Aug. 16, .1960

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mold which serves to illustrate the first step in the process of this invention;

Fig. 2 is a vertical cross section through a mold wherein the first core of Fig. 1 has been replaced with a second core, and illustrating the second step of the process of this invention; and

Fig. 3 is a top perspective view, partially broken away, of a hollow-walled flush tank made in accordance with the present invention as illustrated in connection with Figs. 1 and 2.

Referring to Fig. 1 of the drawings, a plaster mold is designated at 5 which has inserted therein a plaster core 6. The core 6 has a flange 7 extending around the top so as to support it on the top of the mold 5. Accurate registration of the core 6 within the mold 5 is obtained by providing the flange 7 and the top of the mold 5 with mating surfaces as indicated at 8. The mold 5 and the core 6 correspond to and typify the plaster molds which are ordinarily employed for producing single-walled flush tanks and the like, excepting that the mold 5 has a drain hole 15 which is plugged by a plug 16, as will be explained below.

The flange 7 is provided with a hole 10 which registers -with the top of the mold cavity formed between the mold 5 and the core 6. A funnel 11 is inserted into the hole 10 so as to-pour slip into the mold and to fill the mold cavity. It will be understood that the mold is not airtight but it is slip-tight. Accordingly, the slip may be introduced through'the hole 10 so as to fill the mold cavity and the air will be readily displaced out of the mold cavity. After the mold cavity has been filled so as to produce the outer wall or shell of the flush tank as designated at 12, and the mold has set suificiently, the core 6 is removed from the mold 5, leaving the pre-cast outer shell 12 in place therein. This completes the first step or phase of the process.

Thereafter a piece 20 of green clay of suitable size is properly positioned on the bottom of the pre-cast 12 and a second core 13 (Fig. 2) is inserted into the mold 5. The upper part of this core 13 is the same size and shape as the first core 6 so as to rest on the top of the mold S and to fit part-way down into the outer shell 12 to the level or point indicated at 14. Below the level 14 the core 13 is cut inwardly and the main portion of the core 13 below the level 14 is considerably smaller so as to form a relatively wide mold cavity. The bottom surface of the core 13 is also spaced well above the bottom of the mold 5, as shown.

The outer mold 5 is provided with at least one drain hole 15 in the bottom thereof, which hole is normally closed by a plug 16 as mentioned above. After the second core 13 has been put in place, a funnel 17 is introduced into the filling hole 18 therein and the mold cavity it filled with slip. Again, there is suflicient leakage so that the air trapped in the mold cavity is displaced and escapes as the slip is introduced. The slip builds up or sets on the surface of the core 13 and to some extent builds up on the inner surface of the outer shell or Wall 12 which is in the green condition. After the mold has stood for the proper time for the inner wall or shell of the casting to form, as indicated at 21 in Fig. 2, the plug 16 is removed from the drain hole 15 and the liquid slip between the outer shell 12 and the inner wall or shell 21 is drained off, leaving the casting in the condition shown in Fig. 2.

After the second casting step has been completed and the mold has been drained as described above, the second core 13 is removed and thereafter the hollow-walled casting is removed from the outer mold 5. An opening is punched through thebo'ttom of the green hollow casting in register .with the center .of the clay so as to is then fired in the usual way. The finishedhollow-walled tank is shown in Fig. 3 with the inner shell 21 beingjoined at the top to the outer wall or shell 12 by the intermediate portion 22.

It will be noted that the walls of the outershell 12 are considerably thicker than thoseof the inner shell 21 'The outer shell has to have considerable thickness in order to have the necessary strength. According to this invention the walls of the outer shell may be made as thick as desired and necessary, whereas this could not be done'if it were attempted to hollow-castthe tank without first precasting the outer shell. Insofar as I know, this is the first time in the art that anyone has hollow-cast on the inside of a pre-cast using a second core in combination with the same outside mold.

Since certain modifications of an obvious nature may be made in the process described above \m'thout departing from the spirit and scope of'the invention, all matter described above in connection withthe accompanying drawings is intended to be interpreted as illustrative and not in a limiting sense.

What is claimed as new is:

1. The method of producing a hollow-walled vessel which comprises, casting the outer shell by introducing slip into the mold cavity formed between an outer mold and a core, removing said core so as to leave in the outer mold the green casting of said outer shell, inserting a second core into said mold so as to form a mold cavity defining the inner wall of said vessel, filling this latter mold cavity with slip, and draining off the, liquid slip from the interior of the completed casting after the inner wall thereof has formed.

2. The method of producing a hollow-walled flush tank which comprises, casting the outer shell by introducing slip into the mold cavity formed between an outer mold and a core, removing said core so as to leave in the outer mold the casting of said outer shell, inserting a second core into said mold so as to form a mold cavity defining the interior of said hollow-walled vessel, filling this latter mold cavity with slip, allowing the filled mold to stand until the slip has set against the surface of said second core and formed the interior wall of said vessel, and then draining off the liquid slip, from the interior of the last casting while it is still fluid.

3 The method of claim 2 wherein a piece of green clay is placed on the bottom of the outer shell before the second core is inserted, and a hole is made through the bottom of the green hollow casting approximately in registration with the center of said piece of green clay.

4. The method ofproducing a vitreous hollow-walled flush tank which comprises, precasting the outer shell, inserting a core into an outer mold the interior surface of which is formed-by said precast outer shell in green condition, filling the moldcavity formed between said core and said precast outer shell with slip, allowing the filled mold to stand until the slip has set in a layer against interior surfaces of said mold cavity, and draining ofl? the liquid slip from the interior was to leave a hollow casting the outer shell of which has a wall thickness substantially greater than that of the inner shell.

5. A vitreous cast hollow-walled flush tank comprising a relatively thick outer shell and a substantially thinner and lighter weight inner shell non-self sustaining-in the green state integrally joined thereto so as to form a sealedoff dead airspace therebetween', said outer shell having a thickness to sustain itself and the inner shell in the green state and said inner and outer shells being integrally joined at thetops thereof and :at'the-Water connection at the bottom with no connections between the vertical side walls.

References Cited in the file of this patent V UN TED STATES PATENTS 830,243 Magowan Sept. 4, 1906 999,523 Rogers Aug. 1, 1911 1,277,165 Winters Aug. 27, 1918 1,449,761 Kirk et al Mar. 27, 1923 2,277,543 Downs Mar. 24, 1942 2,609,570 Danielson et a1 Sept. 9, 1952 

